There is a neuronal birthdate gradient within the chick optic tectum.

<p>Previous birthdating studies <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079949#pone.0079949-LaVail1" target="_blank">[5]</a> revealed a lateral rostroventral to medial caudodorsal birthdate gradient within the optic tectum. The lateral to medial dimension is not represented here. Taking advantage of this birthdate gradient, we looked for FGF2-induced differences in cell cycle exit in the rostroventral tectum at the beginning of tectal neurogenesis and in the caudodorsal tectum at the end of tectal neurogenesis.